As admin, create a new user and insert the user to any site
As this new user, enter to the site and create an announcement
As an instructor, enter to the site and create another announcement
As admin, delete the user created in step 1
As an instructor, enter to the site an go to "Announcements" -> There is an announcement with no value in "Saved By" column.
Sort announcement by "Saved By" column -> "java.lang.NullPointerException" is thrown.

Description

An exception is thrown when trying to order announcements by a column in which there is a null value.